U.S. patent number 7,763,227 [Application Number 12/441,172] was granted by the patent office on 2010-07-27 for process for the manufacture of carbon disulphide.
This patent grant is currently assigned to Shell Oil Company. Invention is credited to Dean Chien Wang.
United States Patent |
7,763,227 |
Wang |
July 27, 2010 |
Process for the manufacture of carbon disulphide
Abstract
A process for the manufacture of carbon disulfide comprising the
following steps: (a) reacting carbon monoxide with hydrogen sulfide
to form carbonyl sulfide and hydrogen; (b) contacting the carbonyl
sulfide formed in step (a) with a catalyst effective for
disproportionating carbonyl sulfide into carbon disulfide and
carbon dioxide.
Inventors: |
Wang; Dean Chien (Missouri,
TX) |
Assignee: |
Shell Oil Company (Houston,
TX)
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Family
ID: |
37708116 |
Appl.
No.: |
12/441,172 |
Filed: |
September 17, 2007 |
PCT
Filed: |
September 17, 2007 |
PCT No.: |
PCT/EP2007/059746 |
371(c)(1),(2),(4) Date: |
March 13, 2009 |
PCT
Pub. No.: |
WO2008/034777 |
PCT
Pub. Date: |
March 27, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20100028243 A1 |
Feb 4, 2010 |
|
Foreign Application Priority Data
|
|
|
|
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Sep 18, 2006 [EP] |
|
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06120802 |
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Current U.S.
Class: |
423/443; 252/373;
423/648.1; 518/702; 518/700; 423/658.2 |
Current CPC
Class: |
C07C
29/1518 (20130101); C01B 32/72 (20170801); C10G
2/32 (20130101); C07C 29/1518 (20130101); C07C
31/04 (20130101); C01B 2203/062 (20130101); C10G
2300/207 (20130101); C01B 2203/061 (20130101); C01B
2203/84 (20130101); C10G 2300/1025 (20130101); C01B
2203/127 (20130101); C01B 2203/025 (20130101) |
Current International
Class: |
C01B
17/20 (20060101) |
Field of
Search: |
;423/443,648.1,658.2
;252/373 ;518/700,702 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Vanoy; Timothy C
Attorney, Agent or Firm: Hickman; William E.
Claims
That which is claimed is:
1. A process for the manufacture of carbon disulphide comprising
the following steps: (1) providing a hydrocarbon feedstock
comprising hydrogen sulfide; (2) separating at least a portion of
the hydrogen sulfide from the hydrocarbon feedstock: (3) partially
oxidizing at least a portion of the hydrocarbon feedstock from step
2 into a synthesis gas comprising carbon monoxide and hydrogen; (4)
separating at least a portion of the hydrogen from the synthesis
gas from step 3, leaving a carbon monoxide enriched synthesis gas;
(5) reacting carbon monoxide from step 4 with hydrogen sulphide
from step 2 to form carbonyl sulphide and hydrogen; (6) contacting
the carbonyl sulphide from step 5 with a catalyst effective for
disproportionating carbonyl sulphide into carbon disulphide and
carbon dioxide.
2. A process according to claim 1, wherein part of the carbon
monoxide obtained in step 3 is reacted with hydrogen sulphide in
step 5 and the remainder of the carbon monoxide and the hydrogen
obtained in step 3 are used for hydrocarbon synthesis in a
Fischer-Tropsch process or for methanol synthesis.
3. A process according to claim 2, wherein the hydrogen formed in
step 5 is, together with the remainder of the carbon monoxide and
the hydrogen obtained in step 3, used for hydrocarbon synthesis in
a Fischer-Tropsch process or for methanol synthesis.
4. A process according to claim 1, wherein substantially all carbon
monoxide obtained in step 3 is reacted with hydrogen sulphide in
step 5 and the hydrogen obtained in step 3 is used for generation
of electricity in a hydrogen turbine or a fuel cell.
5. A process according to claim 4, wherein the hydrogen formed in
step 5 is, together with the hydrogen obtained in step 3, used for
generation of electricity in a hydrogen turbine or in a fuel
cell.
6. A process according to claim 1, wherein the hydrocarb feedstock
is natural gas.
7. A process according to claim 1, further comprising injecting at
least part of the carbon disulphide formed in step 6 in an oil
reservoir for enhanced oil recovery.
8. A process according to claim 1, further comprising injecting at
least part of the carbon disulphide and carbon dioxide as a mixture
formed in step 6 in an oil reservoir for enhanced oil recovery.
9. A process according to claim 1, further comprising injecting at
least part of the carbon disulphide and carbon dioxide formed in
step 6, together with any unreacted carbonyl sulfide from step 6 as
a mixture in an oil reservoir for enhanced oil recovery.
Description
The present application claims priority of European Patent
Application No. 06120802.1 filed 18 Sep. 2006.
FIELD OF THE INVENTION
The invention provides a process for the manufacture of carbon
disulphide from carbon monoxide and hydrogen sulphide. The process
further results in the manufacturing of hydrogen and carbon
dioxide.
BACKGROUND OF THE INVENTION
Carbon disulphide is typically manufactured by reacting light
saturated hydrocarbons with elemental sulphur that is in the vapour
phase according to the reaction equation:
C.sub.nH.sub.2(n+1)+(3n+1)S.fwdarw.nCS.sub.2+(n+1)H.sub.2S
In GB 1,173,344 for example is disclosed a process for reacting
vapour phase sulphur and propane in the absence of a catalyst under
a pressure not exceeding 10 atmospheres in a reaction zone which is
maintained at a temperature of 550 to 850.degree. C.
In U.S. Pat. No. 3,087,788 is disclosed a process for producing
carbon disulphide from hydrocarbon gas and vaporous sulphur in a
non-catalytic reaction stage combined with, preferably followed by,
a catalytic reaction stage, wherein both stages are operated at a
pressure between 2 and 20 atmospheres and a temperature between 400
and 750.degree. C.
It is also known to manufacture carbon disulphide by catalytically
reacting liquid sulphur with a hydrocarbon. In U.S. Pat. No.
2,492,719 for example is disclosed a process for preparing carbon
disulphide, wherein a suspension of catalyst in molten sulphur is
contacted with a hydrocarbon gas at a temperature of approximately
500 to 700.degree. C., under sufficient pressure to maintain the
sulphur in liquid phase.
A disadvantage of using hydrocarbons as a carbon source for the
manufacture of carbon disulphide is that the hydrogen atoms in the
hydrocarbon react with the elemental sulphur to form hydrogen
sulphide. As disposal of hydrogen sulphide to the atmosphere is
highly undesired and almost always not allowed, expensive treatment
is required, usually by conversion into elemental sulphur. It would
be advantageous to use a carbon source without hydrogen atoms for
carbon disulphide manufacture.
Before 1960, solid carbonaceous material such as charcoal was used
as carbon source for carbon disulphide manufacture. Solid
carbonaceous material was contacted with vaporized elemental
sulphur at very high temperatures. These processes using solid
carbonaceous material were, however, replaced by the
above-mentioned processes using light hydrocarbons such as methane
and propane as carbon source for environmental and safety
reasons.
It is known to use carbon monoxide as carbon source for carbon
disulphide manufacture. In US 2004/0146450, for example, is
disclosed a two-reactor process for the manufacture of carbon
disulphide from carbon monoxide and sulphur dioxide. Two catalytic
reactions are operated in tandem. In a first reactor, carbon
monoxide and sulphur dioxide are reacted in the presence of a
catalyst to form carbonyl sulphide and carbon dioxide. In a second
reactor, the carbonyl sulphide formed in the first reactor is
catalytically converted into carbon disulphide and carbon dioxide.
Carbon disulphide is continuously removed from the second reactor
by a solvent.
Also in U.S. Pat. No. 4,122,156, a two-reactor process for the
manufacture of carbon disulphide from carbon monoxide and sulphur
dioxide is disclosed.
In U.S. Pat. No. 2,767,059 a one-step process is described to
convert H.sub.2S and CO into CS.sub.2. The only product in this
process is CS.sub.2.
In U.S. Pat. No. 4,999,178 a process scheme is described for the
conversion of H.sub.2S into hydrogen and sulphur. The process does
not produce any carbon disulfide. In the first step H.sub.2S is
reacted with a recycle gas comprising H.sub.2S, COS and CS.sub.2
and with a pure CO.sub.2 stream. No reaction between H.sub.2S and
CO is described. The hydrogen produced in the reaction is produced
via the shift-reaction (CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2).
SUMMARY OF THE INVENTION
It has now been found that carbon disulphide can be manufactured
from carbon monoxide by reacting carbon monoxide with hydrogen
sulphide to form carbonyl sulphide and hydrogen and then
disproportionating the carbonyl sulphide formed into carbon
disulphide and carbon dioxide.
Accordingly, the invention provides a process for the manufacture
of carbon disulphide comprising the following steps:
(a) reacting carbon monoxide with hydrogen sulphide to form
carbonyl sulphide and hydrogen;
(b) contacting the carbonyl sulphide formed in step (a) with a
catalyst effective for disproportionating carbonyl sulphide into
carbon disulphide and carbon dioxide.
An advantage of the process according to the invention as compared
to the conventional carbon disulphide manufacturing process using
hydrocarbons as carbon source is that no hydrogen sulphide is
formed that would have to be recycled to a Claus unit for
conversion into sulphur.
An advantage of the process according to the invention as compared
to the known carbon disulphide manufacture processes that use
carbon monoxide as carbon source, i.e. the processes as disclosed
in US 2004/0146450 and U.S. Pat. No. 4,122,156 wherein carbon
monoxide is reacted with sulphur dioxide, is that less carbon
dioxide is co-produced. In the process according to the invention,
one mole of carbon dioxide is co-produced with one mole of carbon
disulphide, whereas in the processes of US 2004/0146450 and U.S.
Pat. No. 4,122,156 five moles of carbon dioxide are co-produced
with one mole of carbon disulphide. In the present process hydrogen
is co-produced which may result in significant design and cost
benefit when used and integrated in other processes.
The process according to the invention has particular advantages
when operated in combination with the conversion of a
hydrocarbonaceous feedstock into synthesis gas, i.e. a gaseous
mixture mainly comprising carbon monoxide and hydrogen. Synthesis
gas is typically produced for subsequent synthesis of hydrocarbons
by the Fischer-Tropsch process, other chemical synthesis processes,
e.g. methanol or ammonia synthesis, power generation in gas
turbines or for hydrogen production. Often, the carbon monoxide to
hydrogen ratio in synthesis gas is too large for the envisaged
application and part of the carbon monoxide in the synthesis gas is
therefore typically converted into hydrogen by subjecting the
synthesis gas to water-gas shift conversion. Another way to solve
this problem is to produce extra hydrogen, e.g. via reforming,
especially steam methane reforming. Combining the process according
to the invention with synthesis gas production has the advantage
that part of the carbon monoxide is used for carbon disulphide
manufacture, thereby decreasing the carbon monoxide to hydrogen
ratio in the remaining synthesis gas to a more desirable level.
Moreover, additional hydrogen is co-produced in the reaction of
carbon monoxide with hydrogen sulphide. This additional hydrogen
can advantageously be used to further decrease the carbon monoxide
to hydrogen ratio of the remaining synthesis gas. The hydrogen made
by the process of the invention may also be used in the upgrading
of heavy oil fractions, e.g. hydrocracking, hydrogenation etc., or
for the generation of electricity.
Another advantage is that hydrogen sulphide is typically available
at synthesis gas production locations, since the hydrocarbonaceous
feedstock typically comprises sulphur compounds. If the sulphur
compound is hydrogen sulphide, such as is the case for sour natural
gas, the hydrogen sulphide will typically be separated from the
hydrocarbonaceous feedstock before gasification. If the feedstock
comprises other sulphur compounds, the feedstock may be
hydrodesulphurized before gasification, thus producing hydrogen
sulphide. A further advantage is that the hydrogen atoms of the
hydrocarbonaceous compound are converted into valuable hydrogen.
The carbon monoxide that is co-produced serves as a hydrogen-free
feedstock for carbon disulphide manufacture and, thus, hydrogen
sulphide formation is avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
In FIG. 1 is shown a process scheme for manufacturing carbon
disulphide and liquid hydrocarbons from sour natural gas.
In FIG. 2 is shown a process scheme for manufacturing carbon
disulphide and hydrogen for electricity generation from sour
natural gas.
In FIG. 3 is shown a process scheme for manufacturing carbon
disulphide, ammonia and ammonium thiocarbonate from sour natural
gas.
DETAILED DESCRIPTION OF THE INVENTION
In the process according to the invention, carbon monoxide is first
reacted with hydrogen sulphide to form carbonyl sulphide and
hydrogen according to: CO+H.sub.2S.fwdarw.COS+H.sub.2 (1)
This reaction is known in the art, for example from U.S. Pat. Nos.
5,609,845 and 6,497,855 B1. The reaction may be carried out in any
suitable way known in the art. Typically, the reaction will be
carried out by contacting gaseous carbon monoxide and gaseous
hydrogen sulphide with a catalyst. Suitable catalysts are for
example those described in U.S. Pat. No. 5,609,845, the disclosure
of which is incorporated herein by reference, for example mixed
metal sulphides, sulphides of transition metals, in particular
silica-supported metal sulphides. Typical reaction temperatures for
step (a) are in the range of from 120 to 750.degree. C.
The carbonyl sulphide formed in step (a) of the process according
to the invention is then contacted in step (b) with a catalyst
effective for disproportionating carbonyl sulphide into carbon
disulphide and carbon dioxide according to: 2COS CS.sub.2+CO.sub.2
(2)
Preferably, the hydrogen formed in step (a) is separated from the
carbonyl sulphide formed in step (a) before the carbonyl sulphide
is disproportionated. This separation may be done by any suitable
conventional technique, for example by selective absorption,
adsorption, rectification or molecular sieving. Pressure Swing
Absorption (PSA) and membrane separation are particular suitable
separation processes. Another suitable method is cryogenic
separation, e.g. low temperature distillation.
Catalysts effective for disproportionation of carbonyl sulphide are
known in the art, for example from US 2004/0146450 and U.S. Pat.
No. 4,122,156. Preferably, the catalyst comprises one or more metal
oxides. Examples of suitable catalysts are alumina, titania,
alumina-titania, silica-alumina, quartz, or clay, for example
kaolin. The catalyst preferably has a specific surface area of at
least 50 m.sup.2/g, more preferably at least 100 m.sup.2/g, even
more preferably at least 200 m.sup.2/g. Particularly preferred
catalysts are gamma-alumina, titania, alumina-titania, or
silica-alumina.
The reaction conditions under which the carbonyl sulphide is
contacted with the disproportionation catalyst may be any reaction
conditions known to be suitable for that reaction, for example the
conditions as disclosed in US 2004/0146450 and U.S. Pat. No.
4,122,156.
Disproportionation reaction (2) is a thermodynamically
unfavourable, reversible reaction. Since the heat of reaction is
close to zero, the equilibrium constant does not change much with
temperature. If desired, the carbonyl sulphide conversion can be
increased by removing carbon disulphide from the reaction mixture,
for example by solvent extraction or condensation.
The carbon monoxide that is reacted with hydrogen sulphide in step
(a) may be carbon monoxide from any suitable source. Preferably the
carbon monoxide is from a synthesis gas stream. Therefore, the
process according to the invention preferably further comprises the
following step:
(c) partially oxidizing a hydrocarbonaceous feedstock to obtain
synthesis gas comprising carbon monoxide and hydrogen;
wherein the carbon monoxide that is reacted in step (a) is carbon
monoxide obtained in step (c).
Partial oxidation of hydrocarbonaceous feedstocks to produce
synthesis gas is known in the art. The hydrocarbonaceous feedstock
may be any suitable feedstock, for example a stream containing
gaseous, liquid or solid hydrocarbons, such as natural gas,
distillate streams, residuum of atmospheric or vacuum distillation
of crude oil, tar sand-derived bitumen, residuum of atmospheric or
vacuum distillation of tar sand-derived bitumen, or coal. Also
lignocellulosic biomass streams, for example wood, straw, corn
stover, bagasse or the like, may be used as hydrocarbonaceous
feedstock.
In the partial oxidation of hydrocarbonaceous feedstocks, synthesis
gas is formed. Synthesis gas mainly comprises carbon monoxide and
hydrogen, and, if air is used as oxidant for the partial oxidation
reaction, also nitrogen. Synthesis gas may comprise minor amounts
of other gaseous compounds, for example carbon dioxide, steam,
hydrogen sulphide, and carbonyl sulphide.
The process according to the invention has particular advantages if
the carbon monoxide that is reacted in step (a) is obtained by
partial oxidation of a hydrocarbonaceous feedstock and the
synthesis gas produced by the partial oxidation is used for
hydrocarbon or methanol synthesis or another application that needs
synthesis gas with a carbon monoxide to hydrogen ratio that is
lower than the ratio obtained by the partial oxidation step. By
using part of the carbon monoxide for the manufacture of carbon
disulphide, the carbon monoxide to hydrogen ratio of the remainder
of the synthesis gas is decreased to a more desirable level. By
adding the hydrogen formed in step (a) of the process according to
the invention to the remainder of the synthesis gas, the ratio can
even be further decreased. Thus, there is no need to convert part
of the carbon monoxide into hydrogen by water-gas shift conversion
and/or to produce additional hydrogen by for example steam methane
reforming.
Therefore, in a preferred embodiment of the invention, part of the
carbon monoxide obtained in step (c) is reacted with hydrogen
sulphide in step (a) and the remainder of the carbon monoxide and
the hydrogen obtained in step (c) are used for hydrocarbon
synthesis in a Fischer-Tropsch process or for methanol synthesis.
More preferably, the hydrogen formed in step (a) is, together with
the remainder of the carbon monoxide and the hydrogen obtained in
step (c), used for hydrocarbon synthesis in a Fischer-Tropsch
process or for methanol synthesis. The above is particularly
relevant for processes starting with feedstocks having a low H/C
ratio, e.g. coal.
Reacting part of the carbon monoxide obtained in step (c) with
hydrogen sulphide may be done by contacting part of the synthesis
gas stream obtained in step (c) with hydrogen sulphide in a reactor
for step (a). Preferably, part of the carbon monoxide in the
synthesis gas stream obtained in step (c) is first separated from
the synthesis gas stream before being reacted with hydrogen
sulphide in step (a). This may be done by separating at least part
of the synthesis gas stream into a stream enriched in hydrogen and
a stream enriched in carbon monoxide. The separation may be carried
out by any suitable means known in the art, for example pressure
swing absorption or membrane separation. The stream enriched in
hydrogen may be substantially pure hydrogen, for example in case a
hydrogen-selective membrane is used for the separation. The stream
enriched in carbon monoxide is then contacted with the hydrogen
sulphide in step (a) of the process according to the invention. The
carbon monoxide concentration in that stream may vary, depending on
the composition of the synthesis gas and the separation method
used. Preferably, the carbon monoxide concentration in the stream
enriched in carbon monoxide is in the range of from 70 to 100 vol
%.
In another preferred embodiment of the invention, substantially all
carbon monoxide that is obtained in step (c) is reacted with
hydrogen sulphide in step (a). Reference herein to substantially
all carbon monoxide is to at least 95 vol % of the carbon monoxide,
preferably at least 99 vol %. The hydrogen obtained in step (c) can
then advantageously be used for applications that need a relatively
pure stream of hydrogen, for example generation of electricity in a
hydrogen turbine or in a fuel cell, or ammonia manufacture. More
preferably, the hydrogen formed in step (a) is, together with the
hydrogen obtained in step (c), used for such applications.
Thus, in a preferred embodiment of the invention, substantially all
carbon monoxide obtained in step (c) is reacted with hydrogen
sulphide in step (a) and the hydrogen obtained in step (c) is used
for generation of electricity in a hydrogen turbine or a fuel cell.
More preferably, the hydrogen formed in step (a) is, together with
the hydrogen obtained in step (c), used for generation of
electricity in a hydrogen turbine or in a fuel cell.
Reacting substantially all carbon monoxide obtained in step (c)
with hydrogen sulphide in step (a) can be done either by contacting
the whole synthesis gas stream obtained in step (c) with hydrogen
sulphide in a reactor for step (a), or by first separating the
synthesis gas stream into a stream enriched in carbon monoxide that
comprises substantially all carbon monoxide formed in step (c) and
a stream enriched in hydrogen. The stream enriched in carbon
monoxide is then contacted with hydrogen sulphide in a reactor for
step (a). In this case, the stream enriched in hydrogen contains
substantially no carbon monoxide and can suitably be used,
optionally after further purification steps, for generation of
electricity in a hydrogen turbine or a fuel cell, manufacture of
ammonia, or in hydroconversion processes for crude oil refining
such as hydrocracking, hydrodesulphurization, hydrogenation, or
other known applications for relatively pure hydrogen.
If the whole synthesis gas stream obtained in step (c) is reacted
with hydrogen sulphide, the hydrogen obtained in step (c) will be
present in the reaction effluent of step (a) together with the
hydrogen formed in step (a). Preferably, the hydrogen in the
effluent is then separated from the carbonyl sulphide and
unconverted reactants and used for an application that needs a
relatively pure stream of hydrogen, optionally after further
purification steps.
The hydrogen sulphide that is reacted with carbon monoxide in step
(a) may be hydrogen sulphide from any source. In case the carbon
monoxide is obtained via partial oxidation step (c), the hydrogen
sulphide is preferably hydrogen sulphide that is either separated
from the hydrocarbonaceous feedstock or obtained from sulphur
compounds in the hydrocarbonaceous feedstock. Hydrogen sulphide may
for example be obtained from such sulphur compounds by
hydrodesulphurization of the feedstock or in partial oxidation step
(c). Also hydrogen sulphide extracted from sour natural gas may be
used.
In a preferred embodiment of the invention, the hydrocarbonaceous
feedstock is natural gas that comprises hydrogen sulphide, i.e.
sour natural gas, and at least part of the hydrogen sulphide that
is reacted with carbon monoxide in step (a) is hydrogen sulphide
that is separated from the natural gas. Separation of hydrogen
sulphide from a hydrocarbonaceous feedstock that comprises hydrogen
sulphide may done by any suitable technique known in the art, for
example by physical absorption in an organic solvent followed by
solvent regeneration.
In step (b) of the process according to the invention, carbon
disulphide and carbon dioxide are formed. The carbon disulphide may
be separated from the carbon dioxide and the unreacted carbonyl
sulphide, for example by condensation or solvent extraction.
Alternatively, a mixture comprising carbon disulphide, carbon
dioxide and unreacted carbonyl sulphide may be obtained. Carbon
disulphide that is separated from the carbon dioxide and the
unreacted carbonyl sulphide may be used for conventional
applications of carbon disulphide, for example as raw material for
rayon production or as solvent.
It is known that carbon disulphide may be used as solvent for
enhanced oil recovery by miscible flooding. In enhanced oil
recovery by miscible flooding, a solvent for oil is introduced into
an oil reservoir and driven through the reservoir to increase oil
recovery from the reservoir beyond what can be achieved by
conventional means. In U.S. Pat. No. 3,847,221 for example, the use
of carbon disulphide for enhanced oil recovery from tar sands is
disclosed.
Preferably, the process according to the invention further
comprises injecting at least part of the carbon disulphide formed
in step (b) in an oil reservoir for enhanced oil recovery. The
carbon disulphide injected may be relatively pure carbon disulphide
that is separated from the carbon dioxide formed and from the
unreacted carbonyl sulphide. For enhanced oil recovery, it is
however not necessary to use pure carbon disulphide. The enhanced
oil recovery solvent may for example comprise a substantial amount
of carbon dioxide. Therefore, the carbon disulphide injected is
preferably in the form of a mixture with carbon dioxide formed in
step (b) and unreacted carbonyl sulphide. Also other liquid
components or streams may be mixed with the carbon disulphide
before the carbon disulphide is injected into the oil
reservoir.
The process according to the invention is particularly suitable for
enhanced recovery of the hydrocarbonaceous feedstock that is used
in partial oxidation step (c). Especially in the case of solid or
semi-solid hydrocarbonaceous feedstocks, such as coal or tar-sand
bitumen, the carbon disulphide that is manufactured may be
advantageously used to recover the hydrocarbonaceous feedstock.
Instead of directly injecting the carbon disulphide formed in step
(b) into an oil reservoir, all or part of the carbon disulphide
formed in step (b) may be first be converted into a salt of a tri
or tetrathiocarbonic acid. Such salt may be then be introduced into
an oil reservoir for enhanced oil recovery under conditions leading
to decomposition of the salt into free carbon disulphide. Enhanced
oil recovery by using salts of tri or tetrathiocarbonic acid is
known in the art, for example from U.S. Pat. No. 5,076,358. In a
preferred embodiment of the invention, part of the carbon
disulphide formed in step (b) is reacted with hydrogen sulphide and
ammonia that is formed with hydrogen obtained in partial oxidation
step (c) and/or carbon monoxide conversion step (a) to form
ammonium thiocarbonate. Ammonium thiocarbonate can for example be
prepared as disclosed in U.S. Pat. No. 4,476,113.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to FIGS. 1 to 3, each schematically showing a process
scheme of an embodiment of the invention, the invention is further
illustrated. For parts of the process that are the same, the same
reference numbers are used as in all three Figures.
In FIG. 1 is shown a process scheme for manufacturing both carbon
disulphide and liquid hydrocarbons from sour natural gas. A stream
of natural gas 1 that comprises hydrogen sulphide, i.e. sour
natural gas, is supplied to a hydrogen sulphide removal unit 2.
Desulphurized natural gas 3 and a molecular oxygen containing gas 4
are supplied to partial oxidation unit 5. In partial oxidation unit
5, the natural gas feedstock 3 is partially oxidised and a
synthesis gas stream 6 mainly comprising carbon monoxide and
hydrogen is obtained. Part 6a of synthesis gas stream 6 is supplied
separator 7 and separated into a gas stream enriched in carbon
monoxide 8 and a gas stream enriched in hydrogen 9.
The gas stream enriched in carbon monoxide 8 is, together with
hydrogen sulphide 10 that is separated from the sour natural gas 1
supplied to reactor 11 for the conversion of carbon monoxide and
hydrogen sulphide into carbonyl sulphide and hydrogen. A mixture 12
comprising carbonyl sulphide and hydrogen formed in reactor 11 is
supplied to separation step 13 and separated into a stream
comprising carbonyl sulphide 14 and hydrogen 15. The hydrogen 15 is
added to gas stream enriched in hydrogen 9 from separator 7 and
combined with the part 6b of synthesis gas stream 6 that was not
sent to separator 7. The combined streams 6b, 9, and 15 are
supplied to a reactor for hydrocarbon synthesis 16 for the
manufacture of hydrocarbons by the Fischer-Tropsch process.
Alternatively, the combined streams 6b, 9, and 15 may be supplied
to a reactor for methanol synthesis (not shown). In another
alternative embodiment of the invention (not shown), streams 6b and
9 are combined and supplied to a reactor for hydrocarbon synthesis
and stream 15 is supplied to a fuel cell or a hydrogen turbine for
electricity generation.
The stream comprising carbonyl sulphide 14 is supplied to
disproportionation reactor 18. In reactor 18, a reaction mixture
comprising carbon disulphide, carbon dioxide and unconverted
carbonyl sulphide is formed. The reaction mixture 19 is withdrawn
from reactor 18. Carbon disulphide may be separated from mixture 19
by conventional separation means (not shown) and then for example
used for enhanced oil recovery. Alternatively, mixture 19 is used
as such as solvent for enhanced oil recovery.
In FIG. 2 is shown a process scheme for manufacturing both carbon
disulphide and hydrogen for electricity generation from sour
natural gas. In the embodiment of the invention as shown in FIG. 2,
the whole synthesis gas stream 6 is separated into separator 7 into
a gas stream enriched in carbon monoxide 8 and a gas stream
enriched in hydrogen 9. The hydrogen 15, i.e. the hydrogen formed
in step (a) of the process in reactor 11 and subsequently separated
from the carbonyl sulphide, is combined with gas stream enriched in
hydrogen 9 and the combined stream is supplied to fuel cell 20 for
electricity generation. Alternatively, the combined stream may be
supplied to a hydrogen turbine (not shown) for electricity
generation.
In FIG. 3 is shown a process scheme for manufacturing carbon
disulphide, ammonia and ammonium thiocarbonate from sour natural
gas.
In the embodiment of the invention as shown in FIG. 3, the whole
synthesis gas stream 6 is separated into separator 7 into a gas
stream enriched in carbon monoxide 8 and a gas stream enriched in
hydrogen 9. The hydrogen 15, i.e. the hydrogen formed in step (a)
of the process in reactor 11 and subsequently separated from the
carbonyl sulphide, is combined with gas stream enriched in hydrogen
9. The combined hydrogen streams and stream of nitrogen 22 are
supplied to ammonium reactor 23 to form ammonia 24. Part 24a of the
ammonia is recovered from the process, for example for use in
fertilizers. Part 24b of the ammonia is reacted with hydrogen
sulphide 25 and carbon disulphide 26 in reactor 27 to form ammonium
thiocarbonate 28. Carbon disulphide 26 is separated from reaction
mixture 19 in separator 29. The remainder 30 of reaction mixture 19
may, if it still comprises carbon disulphide, be used as solvent
for enhanced oil recovery. Alternatively, part of the separated
carbon disulphide 26 is directly injected into an oil reservoir for
enhanced oil recover and part is supplied to reactor 27 for
conversion into ammonium thiocarbonate.
Further process integration may be obtained by using hydrogen
sulphide separated from the sour natural gas 1 in hydrogen sulphide
removal unit 2 as hydrogen sulphide 25 for the ammonium
thiocarbonate manufacture. The nitrogen stream 22 that is supplied
to ammonium reactor 23 may be obtained by air separation (not
shown). The oxygen thus obtained may then be supplied as molecular
oxygen containing gas 4 to partial oxidation unit 5.
* * * * *